Dose related protective effect of azelastine on histamine induced bronchoconstriction in extrinsic asthma.

The effect of single oral doses of the antiallergic agent azelastine hydrochloride (1.1, 2.2 and 4.4 mg) was compared to placebo on airway response to histamine challenge in 12 asymptomatic extrinsic asthmatics with proven bronchial hyperresponsiveness to inhaled histamine in a randomized double-blind crossover trial. All doses of azelastine resulted in a significant protection compared to placebo. The effects of 2.2 and 4.4 mg were equivalent and superior compared to 1.1 mg. A naturally small but statistically significant bronchodilator effect was observed 4 h after the two higher doses of azelastine. Tiredness was reported by two patients, the symptom occurred following each placebo and the active drug.